Big Block Engine Nitrous Tune Up Spark Plug Fuel Ring

Big Block Engine Nitrous Tune Up Spark Plug Fuel Ring

2. The fuel ring is clearly visible on this plug. It’s a dark, sooty, color and stretches almost halfway up the length of the insulator, indicating that this cylinder is running very rich. A clean running cylinder will have a barely visible fuel ring all the way down at the bottom of the insulator.